Power hammer



March 15, 1938. G. L. KOLLOCK 2,110,957

POWER HAMMER Filed July 20, 1936 Patented Mar. 15, 1938 UNITED STATES PATENT OFFICE POWER HAMMER George L. Kollock, Oakland, Calif.

Application July 20, 1936, Serial No. 91,569

8 Claims.A (Cl. Z55-42) My invention relates to power hammers and more particularly to a hammer having a spring presse-d striking head.

It is among the objects of my invention to provide a hammer embodying a striking head actuated by a spring that stressed by means of a cam.

is intermittently Another object of my invention is to provide an arrangement of cams for retracting the striking head to stress the driving spring, without causing the head to bind or causing uneven or undue wearing of the head against adjacent parts.

Another object is the provision in a motor driven hammer of the character described, of driving means for equalizing the lateral thrust on the striking head.

Among other objects of my invention are the provision of improved arrangement of springs for -driving the striking head; improved means for rotating the tool held by the hammer; and safety devices to prevent operation of the hammer unless a tool is in the hammer.

The invention possesses other objects and features oi advantage, some of which, with the' foregoing, will be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species Vof my invention, as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure 1 is a longitudinal sectional view of the power hammer embodying my invention; and

Figure 2 is a similar View of the lower portions of the hammer, taken in a plane indicated by the line 2 2 of Figure 1.

Figure 3 is a transverse sectional view taken in plane indicated by the line 3-3 of Figure 1, and

shows the safety switch.

binding or causing uneven or undue wear.

electric motor is preferably provided for driving the cams, and a safety switch is preferably provided so that the motor may be energized only when a drill or other tool is present in the hammer. Improved means are further provided for rotating a drill held by the hammer.

An iinproved arrangement of springs is also provided for driving the striking head.

In greater detail, an-d referring particularly to Figures 1 and 2 of the drawing, the power hammer embodying my invention comprises a sec- 5 tional housing including a rear cylindrical section 2 and a forward tubular extension 3 fitted in the rear section and secured by a screw il. A suitable handle 6 is mounted on the rear end of the housing, and is preferably provided with a sleeve portion 1 threaded on the end of section 2. The forward end of housing section 3 is prefer'- ably reduced to give the desired pointed nose for convenience in handling the hammer. A demountable cup-shaped tip 8 having an opening 9 for receiving a drill or tool II is preferably provided, and is secured to the housing by suitable screws I2.

Means are provided in the housing for striking the -drill II. For this purpose a cup-shaped 20 striking head I3 is slidably mounted for recipron cation in a bore I4 provid-ed in the forward end of the housing section 3. A backing for the striking head is provided by a narrow rectangular bracket I6 extending across the width of the 25 housing and insertably mounted in grooves Il formed in the side walls of the housing. The bracket is formed in two pieces held together by screws I8 for convenience in assembly; the inner piece of the bracket having a cross partition I9 adjacent the striking hea-d I3, and the outer piece of the bracket having a cross partition ZI carrying lugs 22 for receiving fastening screws 23.

Spring means are provided for driving the striking head against the drill II. Preferably a pair of coaxial springs 2d and 26are provided, the outer spring being seated in the cup provided by the head and compressed between the head and the partition I9 of the bracket. The inner spring 26 is preferably shorter than the outer spring and is held by a groove 2l in the bracket partition I9, so that the free en-d of the spring is spaced from the striking head in the extended position of the latter. This arrangement is superior to a single heavier spring, because both 45 springs are effective at the beginning of the stroke, giving the same initial thrust as a heavier spring; while the single lighter spring with its reduced static inertia is free to give added velocity at the end of the stroke. A greater striking impact is therefore provided.

As shown in Figure 1, the forward end of the striking head I3 is provided with vents 28 to allow free air passage through the head. Shock springs 29 are preferably provided, and are compressed between a shoulder 3l on the housing and a rirn'flange 32 provided on the striking head. rI'he shock springs tend to smooth out the action of the mechanism by helping to initiate a return movement. i

Means are provided for retracting the head i3 to stress the .springs` 2d and This is accomplished by a pair of helical earns 33 arranged side by side in the bracket Iii, and fixed on a pair of substantially parallel cam shafts 3d journaled in the bracket partitions it and 2l. Operable connection between the cams and striking head is made by a pair of arms S6 extending rearwardly from opposite sides of the head and projecting through the partition i9 of the bracket it, so thatl the bracket also functions as a guide for the reciprocating head. The rear ends of the arms 35 each carry a follower roller 31 positioned to ride on the cams The cams 33 are rotated in the same direction, but due to the setting of the followers 3l at relatively opposite sides of the cams as shown in Figure l, undesirable lateral stresses on the head i3 are avoided. The followers il ride up on the inclined faces of the cams to retract the head i3, until the followers ride oir the cam faces; at which time the head is released and driven forwardly by the springs 2d and 25. An important feature of the cam arrangement is that equal lifting forces are applied on opposite sides of the striking head, so that the latter is drawn back uniformly and evenly to prev-ent binding or unven and undue wearing of the sliding parts.

Means are provided for rotating the cam shafts in the same direction to drive the cams. The prime mover for this purpose is preferably an electric motor comprising a field 3d mounted directly in the housing section 2, so that the latter forms the housing ofthe motor. This integral construction in a hammer of the character described is especially important, because it makes a separate motor .housing unnecessary and therefore reduces the weight and bulkiness of the unit. The armature 39 of the motor is journaled at one end in a partition di formed across the forward end of the housing section il, and is journaled at the opposite end in a plate 6?; clamped between the housing section and handle 6. This latter plate also carries the brushes d3 for the motor.

A driving connection between the motor shaft land cam shafts is provided by an intermediate shaft d5 journaled in a yoke il formed on the bracket partition 2 l. As best shown in Figure2, one end of the intermediate shaft @il carries an internal gear d8, which isV connected to pinion d on the motor shaft lll through an idler pinion 5i jcurnaled on the housing partition di. Ihe other end of the intermediate shaft d5 is provided with a helical pinion 52 meshing with helical gears 53 mounted on the ends of the cam shafts 5d. This drive arrangement operates to rotate the cams in the same directionfand also provides a reduction gearing between the motor and cams. The particular reduction used is of course determined by the speed of the motor to be used and the number of driving impulses desirecl of the striking head.

Means are also preferably provided for rotating the drill El during the operation of the hammer. For this purpose a rotor Yis journaled between the end of the housing section 3 and tip 8. This rotoris provided with a hexagonal opening for slidably receiving the hexagonally shaped end of an ordinary drill, so that when the rotor Varm when the drill rotates.

is rotated the drill is also turned. The drill extends freely through the holding rotor 54, and projects through a hole in the end partition 55 of the housing, so as to be engaged by thev striking head i3. As shown in Figure 2, a side shaft 5l is journaled in the housing and extends forwardly alongside the striking head. This shaft carries a pinion 58 on its forward end, meshing with teeth 59 formed on the periphery of the drill holding rotor 54.

The rear end of the side shaft 5l is drivably connected to the intermediate shaft 46 by a short shaft 5I journaled in the housing and having a pinion 2 at one end meshed with a gear 63 on the side shaft. A gear on the other end of the short shaft 6l meshes with a pinion $6 on the intermediate shaft. By this driving arrangement the rotor 5d is rotated simultaneously with the cams et, so that the drill is turned whenever the striking head operates.

Safety means are also preferably provided for preventing operation of the striking head when a drill is not present in the hammer, since operation of the head without the tool in place would cause damage to the hammer. As shown in Figures l and 3, an insulating cup il@ is threaded in the tip 8 ahead oi the rotor 5d. This cup provides a mounting for a pair of normally open spring switch elements El, and a pivoted actuating arm The latter is of arcuate shape to eX- tend over part of the opening so that when drill is inserted the arm is shifted out to press the switch elements together. A stop 59 on the arm limits the inward movement of the arm, and the outward pushing of the arm by the drill may be further assisted by beveling the inner edge of the arm. An important feature of this switch construction is that the curved arm @il enrnore than one of the hexagonal edges of the drill. This prevents chattering of the switch An insulating segment li on the arm t8 prevents contact with the drill.

Suitable leads 'l2 are carried from the handle (i in an external duct 'i3 to the switch elements so that the latter may be interposed in the motor connections. In this way, the motor cannot be energized unless a drill inserted in the hammer. Suitable passages 'ld are provided in the handle i5 for the remaining connections, and

an operating switch 'i6 is also preferably provided in the handle for the convenience of the operator.

A modified form of construction embodying my invention is shown in Figure e. In this oase, the cams 8i are mounted coaxially on a single cam shaft 32 which latter may conveniently comprise a continuation of the intermediate shaft 46 of the structure shown in Figure l. In this tandem arrangement one of the follower arms 83 is longcr than the other, but otherwise the structure is similar Vto that shown in Figure l. The desired result of applying equal pulling forces on opposite sides of Vthe striking head is also obtained with this cam arrangement. So also is the elimination of undesired side thrusts. This is accomplished by the arrangement of the followers 84 on relatively opposite sides of the cams.

VI claim:

1. A power hammer comprising a housing having a shoulder therein, a bracket assembled in said housing and having an end resting against said shoulder, means for fastening the bracket in assembled position, a reciprocable head in the housing, a spring for driving the head, a plurality of coaxial cams journalled wholly in the bracket and independently of the housing for retracting the head to stress the spring, and means for driving the cams.

2. A power hammer comprising a housing, a striking head mounted for reciprocation in the housing, a bracket in the housing, a compression spring for driving the head and interposed between it and the bracket, a cam shaft journaled on the bracket, a cam on the shaft, a follower on the head and riding on the cam for retracting the head to compress the spring, a gear on the cam shaft, an intermediate shaft journaled on the bracket, a pinion on the intermediate shaft and meshed with the cam shaft gear, an internal gear on the intermediate shaft, a motor having its shaft axially aligned with the intermediate shaft, a pinion on the motor shaft, and an idler gear between the motor shaft pinion and the internal gear.

3. A power hammer comprising a housing, a striking head mounted for reciprocation in the housing, a two-part bracket in the housing, means for securing the bracket parts together independently of the housing, means for fastening the bracket to the housing, a compression spring for driving the head and interposed between it and the bracket, a cam shaft journaled on the bracket, a plurality of cams on the shaft, followers on the head and riding on the cams for retracting the head to compress the spring, and means for driving the cam shaft.

4. A power hammer comprising a tubular housing, a striking head reciprocally mounted in the forward end of the housing, a two-part cam bracket mounted in the housing behind said head, means for securing the bracket parts together independently of the housing, means for fastening the bracket to the housing, a thrust spring interposed between the head and bracket, a pair of coaxial cams journaled in the bracket, arms projecting rearwardly from opposite sides of said head, followers on the arms and riding on said cams, and means for driving the cams.

5. A power hammer comprising a tubular housing, a striking head reciprocally mounted in the forward end of the housing, a two-part cam bracket slidably mounted for assembly in the housing behind said head, means for securing the bracket parts together independent ofthe housing, means for fastening the bracket to the housing in assembled position, a cam journaled in the bracket and arranged between the parts thereof, an arm projecting rearwardly from said head, a follower on the arm and riding on the cam, and means for driving the cam.

6. A power hammer comprising a tubular housing having longitudinal grooves therein terminating adjacent the intermediate portions of the housing to provide shoulders, a striking head reciprocally mounted in the forward end of the housing, a cam bracket slidably mounted for assembly in said grooves and having its forward end resting on said shoulders, means for fastening the bracket to the housing in assembled position, a cam journaled wholly in the bracket and independent of the housing, an arm projecting rearwardly from said head, a follower on the arm and riding on the cam, and means for driving the cam.

7. A power hammer comprising a tubular housing having longitudinal grooves therein terminating adjacent the intermediate portions of the housing to provide shoulders, a striking head reciprocally mounted in the forward end of the housing, a rotor journaled in the housing forwardly of the striking head for holding a tool, an elongated two-section cam bracket having a width less than the internal diameter of the housing to provide a space alongside the bracket, said bracket being slidably mounted for assembly in said grooves and having its forward end resting on said shoulders, means for fastening the bracket sections together independently of the housing, means for fastening the bracket to the housing in said assembled position, a cam shaft journaled in the bracket, one end of the shaft being journaled in one section of the bracket and the other end being journaled in the other section, a cam on the shaft, a follower on the head and riding on the cam, a second shaft extending forwardly in the space alongside the bracket for turning the tool holding rotor, and means for rotating said shafts.

8. A power hammer comprising a housing having a shoulder therein, a cam bracket assembled in said housing and having an end resting against said shoulder, means for fastening the bracket in assembled position, a cam journaled wholly in the bracket and independent of the housing, a striking head in the housing, a follower connected with the head and riding on said cam, and means for driving the cam.

GEORGE L. KOLLOCK. 

